A

ITS Report On

220 KV GSS
Submitted in partial fulfillment for the award of the degree of
BACHELOR OF TECHNOLOGY
(Rajasthan Technical University, Kota)
In
Electrical Engineering

SESSION (2021-2025)

Submitted to: Submitted by:

Mr. Atul Sharma
Sunil Kahar
Head of 21EGJEE004
Department

DEPARTMENT OF ELECTRICAL ENGINEERING

GLOBAL INSTITUTE OF TECHNOLOGY,
ITS-1, IT PARK RIICO SITAPURA, JAIPUR-302022

1
 ACKNOWLEDGEMENT

This is my first practical training which has taken at 220 KV GSS, Sanganer.
I would like to express my sincere thanks to Ms. Tarannum Khan, who have given his
excellent guidance and shared his experience with me using entire course of this
training report. We are thanks to other staff member which are guided me. Finally, I
would like to say this summer training has been a valuable part in my life. At last, but
not least I am thankful to the all the staff member of Global Institute of
Technology Electrical Department.

Place: GIT, Jaipur

Student Name: Sunil Kahar

RTU Roll No. :21EGJEE004
B.Tech. VII Semester, IV Year, EE

2
 INDEX
CHAPTERS
1. INTRODUCTION
2. THE YARD
(a) BUS BAR SYSTEM
(b) PROPERTIES
3. LIGHTNING ARRESTOR
(a) SPARK GAPE
(b) NON LINEAR RESISTER
4. WAVE TRAP
(a) LINE MATCHING FILTER AND PROTECTIVE EQUIPMENTS
(b) TRANSMITTER
(c) RECEIVERS
5. ISOLATOR
(a) MOUNTING
(b) EARTH SWITCH
(c) OPERATING MECHANISM
6. INSTRUMENT TRANSFORMER
(a) CORE TYPE
(b) SHELLTYPE
7. POTENTIAL TRANSFORMER
8. CURRENT TRANSFORMER
9. POWER TRANSFORMER
(a) GENERAL
(b) AUTOMATIC CONTROL
10.INSULATOR
11.CIRCUIT BREAKER
(a) FUNCTION OF CIRCUIT BREAKER
(b)

3
 CHAPTER-1

INTRODUCTION

When India becomes independent its overall installed capacity was hardly 1900
mw. During first year plan (1951-1956) this capacity was only 2300 mw. The
contribution of Rajasthan state was negligible during - & 2-year plans the
emphases was on industrialization for that end it was considered to make the
system of the country reliable. Therefore, Rajasthan state electricity board came
into existence in July 1957.

In India electrical power is generated at a voltage of 11KV to 33 KV. which is

taken stepped up to the transmission level in the range of 66 KV to 400 KV

Member of transmission and switching have to be created. These are known as

“SUB STATION”.

Along these transmission lines secondary substation are created where voltage
is further stepped down to sub transmission and primary distribution voltage.

A substation is an assembly of apparatus, which transform the characteristics of

electrical energy from one form to another say from one voltage level to another
level. Hence a substation is an intermediate link between the generating station
and consumer.

For economic transmission the voltage should be high so it is necessary to step

up the generated voltage for transmission and step-down transmitted voltage
for d i s t r i b u t i o n . For this purpose substations are
installed.

4
The normal voltages for transmission are 400kv, 220kv, 132kv and for
distribution 33kv, 11kv etc.
Electricity boards are setup in all states of India which are responsible for
1. Generation
2. Transmission
3. Distribution
They also construct, install and maintain all the station made for this purpose. In
Rajasthan, R.R.V.P.N.L. is responsible for transmission and distribution of electrical
power all over Rajasthan. It has its own generating station and it’s also gets power
from various other stations also. It gets power from following stations: -
1. Badarpur Thermal Power Station Delhi
2. Bhakara Nangl Project (at satlaj in Punjab)
3. Gandhi Sagar Dam Kota
4. Jawahar Dam Kota
5. Rana Pratap Sagar Dam Kota
6. Rajasthan Atomic Power Plant (RAPP) Kota
7. Kota Super Thermal Power Station (KSTPS) Kota
8. Anta Gas Power Plant Anta
9. Rajasthan share in Bhakara Beas Management Board (BBMB)
Power obtain from these stations is transmitted all over Rajasthan with the help of grid
stations. Depending on the purpose, substations may be classified as: -
1. Step up substation
2. Primary grid substation
3. Secondary substation
4. Distribution substation
5. Bulky supply and industrial substation
6. Mining substation

5
7. Mobile substation
8. Cinematograph substation
Depending on constructional feature substation are classified as:-
1. Outdoor type
2. Indoor type
3. Basement or Underground type
4. Pole mounting open or kilos type

Any substation has many types of civil and electrical works. Main compo
nets are:-
 Bus bar
 Power transformers
 Isolators
 Circuit breaker
 Lightening arrester
 Insulators
Instrument transformers
The control room is equipped with protective relays, ammeters, voltmeters,
energy meters and frequency and power factor meters
D.C. supply is heart of GSS batteries are used for this purpose. They have
separate charging circuit also. For communication purpose P.L.C.C. is used
which has its various components.
220 KV GSS, Sanganer is the part of the transmission system.

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INCOMING FEEDER:
 400 KV Heerapura- Sanganer,
 220 KV Kota –Sanganer
 220 KV Heerapura-Sanganer

OUTGOING FEEDER: -
 132 K.V.
1. Balawala
2. Heerapura
3. Mansrovar
4. SMS Stadium
5. Chaksu
6. Sitapura

 33 K.V.
1. Durgapura I & II
2. Sanganer
3. Sitapura
4. Muhana Mandi
5. Malpura Gate
6. Vatika
7. Phagi
8. IOC
 11 K.V.
1. Tajawal
2. muhana
3. Prem Nagar

7
 CHAPTER-2

THE YARD
The yard is spread in very long area. The yard of 220 KV GSS at Sanganer has various
equipment installed at the yard of 220 KV GSS, Sanganer are:-

 Lighting Arrester
 Wave Trap
 Current Transformer
 Circuit Breaker
 Bus Bars
 Power Transformer
 Insulator
 Potential Transformer
 Static earthling system
 PLCC equipment including coupling capacitance
 Bushing
 Isolator

Figure-2.1 Switch Yard

8
 BUS BAR SYSTEM

This bus bar arrangement is very useful for working purpose as every GSS.
It is a conductor to which a number of cut .Are connected in 220 KV GSS there
are two bus running parallel to the each other, one is main and another is
auxiliary bus is only for stand by, in case of failure of one we can keep the
supply continues.

If more loads are coming at the GSS then we can disconnect any feeder
through circuit breaker which is connected to the bus bar. This remaining all the
feeders will be in running position .if we want to work with any human damage.
In this case all the feeders will be on conditions.

According to bus voltage the material is used .Al is used because of the
property & features and it is cheap.

With the help of bus bar arrangement we can connect all the incoming
supply which is coming from different higher order GSS.

9
 PROPERTIES

COPPER ALUMINIUM

1. Electricity resistively at 20 c

0.017241

0.00403

2. Temp coff. Of

resistively 0.00411

0.00403

3. Softening tem.

200

180

4. Thermal conductivity

.932

.503

5. Meting point

1083

657

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 CHAPTER-3

LIGHTENING ARRESTER

Lightening arrester is first equipment of GSS. It is protecting all the

equipment against the HV. The ground wire or earthing does not
provide protection against the high voltage waves reaching the terminal
equipment .so some protective device is necessary to produce power station
,sub-station and transmission lines against the high voltage wave reaching here.
Which is connected between line and earth it acts as a safty valve. .

Through the surge impedence of line limits the amplitude of the line to
earth over voltage to a value which wills safe guard the insulation of the
protected equipment.

An ideal L.A should have following characteristics:-

1. It should not take any current under normal condition .i.e. its spark
over voltage must be higher then the system voltage.
2. Any abnormal transient voltage above the break down voltage must
caused it to break as quick as possible in order to provide an alternate path to
earth.

11
3. It must be able to carry the resultant discharge current without
causing damage to itself.

For high voltage system the thirties type L.A are used .The value type is
also known as non linear diverter .These arrester consist of a spark gape and a
non linear resistance. Both resistance and spark gape are accommodated in
series with a completely light porcelain condition humidity etc.

SPARK GAPE:-

They include a number of identical elements connected in series .Each

element consist of with pre ionization device between each grounding resistance
of high ohmic value connected in parallel.

3.3 NON LINEAR RESISTER:-

The resister disc comprises inorganic material having a silicon carbide base
in a clay board. These discs form a block. The ohmic value of which decreases
rapidly when the applied voltage and current increases as soon as the current
wave resulting from the over voltage has been discharged. The resister block
subjected to the sole. Alternating Voltage and resistance assumes great value
.So that the amplitude of the resulting current becomes zero.

12
Figure-3.1 Lighting Arresters

13
 CHAPTER-4
WAVE TRAP

It is used to trap the communication signals & send PLCC room through
CVT.

Rejection filters are known as the line traps consisting of a parallel resonant
circuit ( L and C in parallel) tuned to the carrier frequency are connected in
series at each and of the protected line such a circuit offer high impedance to the
flow of carrier frequency current thus preventing the dissipation. The carrier
current used for PLC Communication have to be prevented from entering the
power equipments such as attenuation or even complete loss of communication
signals. For this purpose wave trap or line trap are used between transmission
line and power station equipment to-

Avoid carrier power dissipation in the power plant reduce cross talks with
other PLC Circuits connected to the same power station.

Ensure proper operating conditions and signal levels at the PLC transmit
receive equipment irrespective of switching conditions of the power circuit and
equipments in the stations.

Line Matching Filter & Protective Equipments

For matching the transmitter and receiver unit to coupling capacitor and power
line matching filters are provided. These flitters normally have air corral
transformers with capacitor assumed.

The matching transformer is insulated for 7-10 KV between the two windings
and perform two functions. Firstly, it isolates the communication equipment
from the power line. Secondly, it serves to match .

14
 Figure-4.1 Line Matching Filter & Protective Equipments

Transmitter

The transmitter consists of an oscillator and a amplifier. The oscillator

generates a frequency signal with in 50 to 500 HZ frequency bands the
transmitter is provided so that it modulates the carrier with protective signal.
The modulation process usually involves taking one half cycle of 50 HZ signal
and using this to create block to carrier.

Receivers

The receivers usually consist of and alternate matching transformer band

pass filter and amplifier detector.

The amplifier detector converts a small incoming signal in to a signal

capable of operating a relatively intensive carrier receiver relay. The transmitter
and receiver at the two ends of protected each corresponds to local as far as
transmittion

15
 CHAPTER-5

ISOLATER:-

When carrying out inspection or maintains work in substation ,it is essential

to disconnect reliability the unit of other station on which the work is done from
all other parts on installation in order to ensure full safety of working staff .So
guard against mistake it is desirable that should be done by an apparatus is
called “ISOLATOR”. In other words a device which is used to open or close the
circuit either when negligible current is interrupted or when no significant
change in voltage across the terminal of each pole of the isolator will result
from operation
.they must only be opened or closed when current is zero. There is single ear
thing Isolator used .

Isolator is switching device used to open (or close) a circuit either when a
negligible current exists or when no significant change in voltage across the
terminal of each pole of the isolator, will result from the operation.

Broadly speaking isolator are the switches which’s operate under "No
current” condition. Thus, isolator is an apparatus which makes a visible and
reliable disconnection of the unit or the section after opening the circuit breaker.

Isolators are file with earthing blades as an integral part of it. They may be
isolators with single ear thing blades or two earthling blades on either side of it.
The isolators used at 220 KV GSS, Sanganer have single earthing blades either
side of it.They must only be opened or closed when current is zero. Isolators are
classified into following categories.

1. Bus isolator
2. Line isolator
3. Transformer isolating switch
16
From constructional point of view the isolator may be classified as-

1. The post- centre post rotating part, double post break type.

2. Two post single type.

3. Base: - Each pipe phase isolator is mounted on a robust base of steal

construction.

Figure- 5.1 Isolator

17
MOUNTING: -

The central post rotates in gun metal bushing and tapered roller bearing
provided with grease nipples for lubrication required to be alone at regular’s
intervals during routine check up.

EARTH SWITCH:-

(For line side insulation only ) Earthling is achieved by means of an earthed

blade pivoted at the base steady operation mechanism .the earth contacts are
fixed either at the back or left or right side of main contact and interlocked
with them by mechanism interlock.

OPERATING MECHANISM:-

1. Hand operated: - It consists of a fulcrums and level system for easy operation
of isolators.

2. The isolators used in G.S.S Sanganer at are three post types. Each isolator has
three insulators post per phase mounted on a phase of steal construction.

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 CHAPTER-6

INSTRUMENT TRANSFORMER

The transformers which are used in A.C. system for the measurement of current,
voltage, power and energy are called Instrument transformer. These are also
used in connection with the measurement of power factor, frequency and for
indication of synchronism.They are two types namely:

1. Current transformer

2.Potential transformer.

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 Figure-7.1 POWER X-MER

(1) Core type

(2) Shell type

The x-mer used substation is auto-transformer which employed only single

winding per- phase. A part of winding is common to both of sides. In addition
to primary and secondary winding known as tertiary winding is also provided
the power transformer required at substations contain following additional part
–

1. HV winding bushing

2. LV winding bushing

3. Tertiary winding bushing

20
 4. Jucking plate

Transformer used in conjunction with measuring are ‘INSTRUMENT

TRANSFORMER’. According to the quality measured. These may be
divided as

1. Current transformer

2 Potential transformer

These instrument transformers are used to step down these current and voltage.
So that they would be metered with instrument of moderate size.

21
 CHAPTER-7

CURRENT TRANSFORMER

The current transformers are kept in the category of the instrument

transformer. The C.T. are used to reduce/ stepping down A.C form high value to
lower value for measurement / protection / control.

They are usually installed in the out door switch. The primary conductor at
high voltage with respect to earth. The secondary of C.T. is just like the ring
type
C.T. the primary winding consists of a very few turns , and therefore there is no.
appreciation volt drop across injection . Current is transformed by C.T. the
current transformer is used with primary winding , connected in series with the
line carrying the current to be measured and therefore primary current is
dependent upon load connected in the system.

22
 Measurement of alternating current is one of the most frequent operation not
only because of it’s inheriant but a also because it is necessary in determining
other parameters of electrical circuit. A current transformer value of current is
used for Indication of current kwh and kw meters Telementry Protective relay
etc

A current transformer is intended to operate normally with rated current of

the system flowing through the primary winding which is increased in the series
with the network .Secondary winding of current transformer Connected to
measuring instruments and relay supplies currents circulating in the design of
current transformer.

POTENTIAL TRNASFORMER

Similar to CT it is another type of instrument type of instrument transformer

.Transformer used for voltage measurements are called voltage transformer or
Potential transformer. it may be of 1 phase or 3 phase

23
 These transformers make the instruments suitable for measurement of high
voltage and isolating then from high voltage. these transformer are connected in
parallel and secondary winding is always open ckt.

The primary winding of the potential transformer is connected to the main

GSS LINE DIAGRAM. the primary has large no of turn in secondary,which
provided step down of voltage , and then the voltmeter is connected across
secondary terminal the high voltage line.

Some terms related to PT :-

A. RATED VOLTAGE :- the capacity voltage of the PT

which it can stand
B. RATED TRARNSFORMER RATIO:- The ratio of the rated
primary voltage to the rated second voltage.
C. RATED SECONDARY VOLTAGE:- 130 / root (3) = 63.3
VAR.
Voltage transformer which step down system voltage to sufficient form
high value to low value are necessary in every system for

Induction of d.c supply voltage conduction.

Metering of the supply of energy.

Relaying

Syncronizing.

Design and ranges are selected according to the secondary size of potential
transformer for indicating instruments, meter and relays. But calibration of
these
instruments is done according to the primary voltage .

24
`

25
 CHAPTER-8

POWER TRANSFORMER

GENERAL:-

The transformers are used to step down or step-up the incoming line voltage
but at grid substation for the purpose of distribution. it is the main & major

26
requirement of GSS for step down the supply voltage .The rating of transformer
is taken according to the load .

There are two power transformers of 100 MVA . They are used convert 220
KV/132 KV. And two power transformers are used of 20/25 MVA .which
convert 132KV/33KV. Which transforms e/e energy from one voltage level to
another desired level with corresponding change in current value and with out
any change in frequency value.

The physical basis of a transformer is mutual induction between the circuits

linked by a common magnitude pulse voltage supplied to one set of winding
called primary switch builds up a magnitude flux through the iron.

A transformer in simplest form consist of two magnetic coil, which are

electrically separated from each other but magnetically linked through path of
reluctance .

In brief a transformer is a device that

1. Transform electric power from the one circuit to another.

2. It does not so without a change of frequency.

3. It accomplishes this by electromagnetic induction.

The magnetic core is built up of laminations of high –grade section or other

steel which are insulated from each to other by varnish or other insulation
materials.

According to the number of winding placed around the core. The

transformer are classified as

5. Earthing terminals the trank

27
 6. Cooling systems

7. Pressure relief value

8. Bush hold relay

9. Dehydration breather

10. Rollers

11. Filters

Automatic control:-

The automation required use of automatic voltage control of substation so

that a predetermined bus- bar voltage can maintained. In general a tap changer
is provided on a transformer for a maintaining a pre determine outgoing voltage
where the incoming voltage may be subjected to voltage variations. The output
of P.T. connected to controlled voltage side of the power of transformer is used

28
to energize the automatic voltage regulating relays. The voltage to be controlled
remains with in prescribed limits.

GAS OPERATED RELAY:-

The relay is located in the pipe between the main tank and conservator. In
case of fault such as insulation was creating impulse failures fall of oil level
produces gases. This rises and accumulated in the upper part of the housing
consequently the oil level falls down and the float sinks thereby tilling the
mercury switch. The conducts are closed and alarm circuit is energized.
Bachholz protection is always used in conjunction with some other forms of
electricity operated protective gears as it can unity operate for truly internal
transformer faults and does not respond to external bushings or cable faults.

SILICA GEL BREATHER:-

A silica gel breather is employed as a measurement of preveusing moisture

in gress. It is connected to the conservator tank which is filled to transformer to
allow for changes in volume due to temperature variation.

FILTER: - Filter is intended for prolonging like water acid etc from oil. .

29
 TRANSFORMER OIL:-

In transformer, the insulating oil provides an insulating medium as well as a

heat transferring medium that carry away heat produced in the winding and iron
core.

The life of the transformer depends chiefly upon the quality of the
insulating oil. So high quality insulating oil are used. It should meet the
following requirements:-

 It should be provide good transfer of heat.

 It should provide high electric strength.
 It should have low velocity.
 Flash point of the oil must be high.
 Also fire point should be high.

30
31
 INSULATORS

In order to avoid current leakage to the Earth, through the supporting

structure provide to the conductor of overhead transmission lines, insulators are
used. The conductors are secured to the supporting structures by means of
insulating feature, which do not allow current to flow through these support and
hence finally to the earth . Bus support insulators are porcelain or fiberglass
insulators that serve to the bus bar switches and other support structures and to
prevent leakage current from flowing through the structure or to ground. These
insulators are similar in function to other insulator used in substations and
transmission poles and towers.

An Insulator should have following characteristic:-

1. High Insulation resistance.

2. High mechanical strength
3. No internal impurity or crack Disc

Generally Porcelain or glass is used as material for insulators. Porcelain

because of its low cost. is more common.

Insulators can be classified in following ways :-

Pin Type: - These are designed to be mounted on a pin, which in turn is

installed on the cross arm of a pole.

32
 Figure-8.1 INSULATORS

Suspension Type:-These insulators hang from the cross arm, there by forming
a string.

The centre post carries the moving contact assembled at the extremities the
moving contact engages the fixed contacts are generally in the form of spring
loaded finger contact.

33
 The insulator consist of following parts -

1. Contacts :- The contacts are rated for line current and designed to
withstand electromagnetic strains and prevent charging at rated shortly time
current the contact are made of electrolytic fixed in housing.

2. Switching blade:- The blade is made of electrolytic copper.

3. Tandom pipe:-All three phases are opened or closed simultaneously with a

tandem pipe this is dipped galvanized and provided with on or off insulators and
pad locking.

4. Motor operated:-This is meant rotary motion of the linear operating pipe for
either of opening or closing for remote level local operation. Hand operation is
also provides with detectable handle that can be fitted and square.

34
 CHAPTER-9

CIRCUIT BREAKERS:-

Breakers are switching and current interrupting devices. Basically a

circuit breaker comprises a set of fixed and movable contacts. The contacts can
be separated by means of an operating an arc. The arc is extinguished by a
suitable medium such as dielectric oil vacuum, SF6 gas.

The circuit breakers play an important role in the design and performance
of a power system, in that these are the key pieces of apparatus protecting the
system and thus ensure continuity of supply from consideration of cost, the
circuit breakers represent a major items, and are, next only to the generator and
transformer, since their quantity is greater than that of generators/transformer in
a power system owing to the services required for control of transmission lines,
bus-bar etc. in addition to control of transformers and generator.

Figure-9.1 CIRCUIT BREAKERS.

FUNCTION OF CIRCUIT BREAKER

The expected functions of a circuit breaker are: -

35
 i. It must be capable of closing on to and carrying full load currents for long
period of time.
ii. Under proscribed condition, it must open automatically to disconnect the
load or some small overload.
iii. It must successfully and rapidly interrupt the heavy current, which flow
when a short circuit has to be cleared from the system.
iv. It must be capable of closing on to a circuit in which a fault exists and
immediately re-opening to clear the fault from system
v. It must be capable of carrying current of short circuit magnitude until,
and for such time as, the fault is cleared by another breaker nearer to the pint of
fault.

Circuit Breaker Types

i. Bulk oil Circuit Breakers

ii. Minimum oil Circuit Breakers.
iii. Air blast Circuit Breakers
iv. Sulphur hexafluoride (SF6) Circuit Breakers.
v. Vacuum Circuit Breakers

AIR BLAST CIRCUIT BREAKER

This type of breaker find application operating system from 132 kv and
these are meant for outdoor used and based on the multiple interception.
Principal using compressed air as a medium for quenching the arc. The
compressed air acts as a medium of high dielectric strength which present
flashover across the writers in case of over voltage when the contacts are in

36
 open position. The breaker can be opened or closed pneumatically from the
control cabin or by protective relay or electrically fault occuring the operating
pressure used at G.S.S Sanganer is 12 kg/cm.

AIR BLAST C.B. HAS FOLLOWING ADVANTAGES:-

1. No fire hazards caused by oil.

2. The C.B operates at hogs speeds.
3. The duration of arc is possible.
4. Frequent operation of C.B’s is possible.
5. Almost no maintenance is needed.
6. Facility of high speed recoding.

TYPES OF AIR BLAST C.B’s:-

There are three types of air blast circuit breaker:-

1. Axial blast C.B.

2. Axial blast air C.B. and with side moving contact.
3. Cross blast air circuit breaker.

OPERATION:-

In the closed position of air blast circuit breaker. There is no

compressed air in arc chamber hallow calcium insulator. When fault occurs on
the line CB operates and compressed air quenches the arc into no of section.

37
 VACUUM CIRCUIT BREAKER

FUNCTION OF SF6 GAS IN SF6 CIRCUIT BREAKERS

The density of SF6 Gas is about five times that of air and heat dissipation in it
is also much more than in air.

Air atmospheric pressure dielectric strength of SF 6 gas is about 2.4 times

that of air and at about 3-Kg/cm2 it is same as that of oil. Table no. D1 gives
physical properties of SF6 gas.

There is some decomposition of the gas long periods of arcing. However

such decompositions very little and has no effect upon dielectric strength and
interrupting capability. The solid are product formed by arcing metallic fluoride,
which appears in the form of fine gray powder. This are generated power has
high dielectric strength under dry conditions existing in the breaker. A good
quality absorbent is used so that the level of the gaseous by products is kept
very low. Certain impurities such as air result in the dilution of SF 6 gas in the
field as long as the process recommended is followed. While releasing the arced
gas into atmosphere, international sniffing of gas should be avoided. The
relation between SF6 gas pressure and temperature is given in fig. 4.13, which is
a very useful date at the tie filling of SF6 in circuit breaker.

38
Figure-9.2 SF6 CIRCUIT BREAKERS

39
 CHAPTER -10

EARTHING

Earthing is the provision of a surface under the sub station, which has a
uniform potential as nearly as zero or equal to Absolute Earth potential. The
provision of an earthing system for an electric system is necessary by the
following reason.

1. In the event of over voltage on the system due to lighting discharge or other
system fault. These parts of equipment which are normally dead as for as
voltage, are concerned do not attain dangerously high potential.

2. In a three phase, circuit the neutral of the system is earthed in order to

stabilize the potential of circuit with respect to earth.

The resistance of earthing system is depending on shape and material of

earth electrode used.

The earthing is of two principal types :-

 Neutral Earthing
 Equipment Body Earthing

40
 Neutral Earthing:-

Neutral Earthing also known as System Neutral Earthing (or Grounding)

means connecting the neutral point i.e. the star point of generator,transformer
etc. to earth. In rotating machines, generator, transformer circuit etc., the neutral
point is always connected to earth either directly or through a reactance. The
neutral point is usually available at every voltage level from generator or
transformer neutral. If neutral point is not available, then the most common
method used is using a Zigzag transformer. Such a transformer has no
secondary. Each phase of primary has two equal parts. There are 3 limbs and
each limb has two winding, providing flux density under normal condition.
Since the fluxes are opposite, the transformer takes very small magnetizing
current under normal conditions. During fault, the circuit is primary side,

which provides very less impedance to the current. The grounding

transformers are short time rating. Their size is almost one tenth as compared to
power transformer.

41
 Electrical Earthing:-

Electrical Earthing is different from neutral earthing. During fault

condition, the metallic parts of an electrical installation which do not carry
current under normal conditions, may attain high potential with respect to
ground. As human body can tolerate only I=0.165A/T current for a given time t
so to ensure safety we connect such metallic parts to earth by means of Earthing
system ,which comprises of electrical conductor to send fault current to earth.
The conductor used is generally in the form of rods, plates, pipes etc.

Earthing system ensures safety in following ways :-

1. The potential of earthen body does not reach dangerously high value
about earth, since it is connected to earth.
2. Earth fault current flows through earthing and readily causes the
operation of fuse or an earth relay.

42
Connection of Electrical Equipment to Substation:-

S.NO. Apparatus Path to be connected

1. Supporting of bus Base plate
insulator
2. High voltage circuit Operating mechanism
breaker frame
3. Isolator Operating mechanism
frame bed
4. Potential transformer Transformer tank LV
5. Power transformer Core tank

Merits of neutral Earthing:-

1. Arcing grounding is reduced.

2. Voltage of heating with respect to earth remains at harmless value they don't
increase to root 3 times of normal value.

3. Suitable neutral point.

4. The earth fault relaying is relatively simple useful amount of earth fault
current is available to operate earth fault relay.

5. The over voltage due to lightening are discharged to earth.

6. Improved service reliability due to limitation of arcing ground and improved

of unnecessary fringing of CB.

At GSS the neutral point of power transformer is connected solidly to earth

generally the earth connection are provided which leads reliability.

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 CHAPTER-11

Power Line Carrier Communication :-

Introduction

Power Line Carrier Communication (PLCC) provides for signal

transmission down transmission line conductors or insulated ground wires.
Protection signaling, speech and data transmission for system operation and
control, management information systems etc. are the main needs which are met
by PLCC.

PLCC is the most economical and reliable method of communication

because of the higher mechanical strength and insulation level of high voltage
power line which contribute to the increased reliability of communication and
lower attenuation over the larger distances involves.

High frequency signals in the range of 50 KHZ to 400 KHZ commonly

known as the carrier signal and to result it with the protected section of line
suitable coupling apparatus and line traps are employed at both ends of the
protected section. Here in Sanganer and also in other sub-station this system is
used. The main application of power line carrier has been from the purpose of
supervisory control telephone communication, telemetering and relaying.

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 PLCC Equipment

The essential units of power line carrier equipment consists of :-

a. Wave trap
b. Coupling Capacitor
c. LMU and protective equipments.

MERITS AND DEMRITS OF PLCC

Merits

The severity that a power line can withstand is much more than that odd
communication line due to higher mechanical strength of transmission line
power lines generally provide the shortest route between the Power Station and
the Receiving Stations.

The carrier signals suffer less attenuation, owing to large cross sectional area of
power line

Larger spacing between conductors reduces the capacitances which results in

lesser attenuation of higher frequencies.

Large spacing also reduces the cross talk to a certain extent.

The construction of a separate communication line is avoided.

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Demerits

Utmost care is required to safeguard the carrier equipment and persons using
them against high voltage and currents on the line.

Noise introduced by power line is far more than in the case of communication
line. This is due to the discharge across insulators and corona etc.

Induced voltage surges in the power line may affect the connected carrier
equipment.

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 CONCLUSION

The training at grid substation was very helpful. It has improved my theoretical
concepts of electrical power transmission and distribution. Protection of various
apparatus was a great thing. Maintenance of transformer, circuit breaker,
isolator, insulator, bus bar etc. was observable.
I had a chance to see the remote control of the equipment’s from control room
itself, which was very interesting.
So, the training was more than hope to me and helped me to understand about
power system more.

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